[移动开发]Android，Retrofit+RxJava网络框架的使用

1. 说明

Retrofit+RxJava这套组合的网络框架在Android开发中还是相对好用的，本文根据自身实验简要说明一下其用法。若有大佬路过，发现其中不妥，还请指出。

2. 用法

Step1: 建立后台返回的JSON数据

    private Integer status;     //状态码
    private String message;     //返回信息
    private Object obj;         //返回对象

Step2: 前端接受的基本数据类型

    private int status;				
    private String message;
    private T obj;

这里需要注意：
（1）前后端的对应参数名一定要对应，例如：status 对应 status.
因为前端是通过GSON去进行解析，如果参数名不对应，最后解析不了。
（2）后端的obj如果传输的是Bean实体类，那用前端用来的接受的Bean的实体类里面的参数名一定要和后端的实体类的参数一一对应。

Step3：android端导入依赖（后面步骤都是在android端了）

（1）引入RxJava和Retrofit依赖

    // Rxjava
    implementation "io.reactivex.rxjava2:rxjava:2.2.6" // 必要rxjava依赖
    implementation "io.reactivex.rxjava2:rxandroid:2.1.0" // 必要rxandrroid依赖，切线程时需要用到
    // Retrofit
    implementation 'com.squareup.retrofit2:retrofit:2.8.1' // 必要retrofit依赖
    implementation 'com.squareup.retrofit2:converter-gson:2.8.1' // 必要依赖，解析json字符所用
    implementation 'com.squareup.okhttp3:logging-interceptor:4.9.0' //非必要依赖，log依赖，如果需要打印OkHttpLog需要添加
    implementation 'com.squareup.retrofit2:adapter-rxjava2:2.5.0' // 必要依赖，和rxjava结合必须用到

（2）在AndroidManifest.xml中加入网络权限

    <uses-permission android:name="android.permission.INTERNET"/>

Step4：先写统一的异常处理类

public class ServerException extends Exception {
    private int code;
    public ServerException(String message){
        super(message);
    }

    public ServerException(int code, String mes){
        super(mes);
        this.code=code;
    }

    public int getCode(){
        return code;
    }

    @Override
    public String toString(){
        return "ServerException{"+
                "code="+code+
                '}';
    }
}

Step5: RxJava对网络返回请求的统一处理

//RxJava对网络请求的统一处理
import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.ObservableSource;
import io.reactivex.ObservableTransformer;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.functions.Function;
import io.reactivex.schedulers.Schedulers;

public class RxHelper {
    //去壳处理
    public static <T>ObservableTransformer<BaseResponse<T>,T>  handleResult(){
        return new ObservableTransformer<BaseResponse<T>, T>() {
            @Override
            public ObservableSource<T> apply(Observable<BaseResponse<T>> upstream) {
                return (ObservableSource<T>) upstream.flatMap(new Function<BaseResponse<T>, ObservableSource<?>>() {
                    @Override
                    public ObservableSource<?> apply(BaseResponse<T> tBaseResponse) throws Exception {
                        int code=tBaseResponse.getStatus();
                        String desc=tBaseResponse.getMessage();
                        T data=tBaseResponse.getObj();
                        //Log.e("CTB_RxHelper: ", data.toString());
                        if(code==ServiceFactory.NET_SUCCESS_CODE){
                            return createObservable(data);
                        }else{
                            return Observable.error(new ServerException(code,desc));
                        }
                    }
                }).subscribeOn(Schedulers.newThread())
                        .observeOn(AndroidSchedulers.mainThread());
            }
        };
    }

    // 创建指定数据源的Observable
    // 即：将后端传来的数据，如果为空，则则直接走 onComplete(); 否则，走onNext()，即传数据
    private static <T> Observable<T> createObservable(final T t) {
        return Observable.create(new ObservableOnSubscribe<T>() {
            @Override
            public void subscribe(ObservableEmitter<T> e) {
                if (e != null) {
                    if (t != null) {
                        e.onNext(t);        // 到observe的onNext()
                    }
                    e.onComplete();
                }
            }
        });
    }
}

Step6: OKHttpClientFactory类

//okHttp设置
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.concurrent.TimeUnit;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

import okhttp3.OkHttpClient;

@SuppressWarnings("deprecation")
public class OKHttpClientFactory {
    private static OkHttpClient defaultClient;

    public static OkHttpClient getDefaultOkClient()  {
        SSLSocketFactory socketFactory=null;
        if(defaultClient==null){
            synchronized (OKHttpClientFactory.class){
                if(defaultClient==null){
                    final TrustManager[] trustAllCerts=new TrustManager[]{
                            new X509TrustManager() {
                                @Override
                                public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {

                                }
                                @Override
                                public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {

                                }

                                @Override
                                public X509Certificate[] getAcceptedIssuers() {
                                    return new X509Certificate[]{};
                                }
                            }
                    };
                    try{
                        SSLContext sslContext=SSLContext.getInstance("SSL");
                        sslContext.init(null, trustAllCerts, new java.security.SecureRandom());
                        socketFactory = sslContext.getSocketFactory();
                    } catch (NoSuchAlgorithmException e) {
                        e.printStackTrace();
                    } catch (KeyManagementException e) {
                        e.printStackTrace();
                    }

                    HttpLoggingInterceptor httpLoggingInterceptor = new HttpLoggingInterceptor();
                    httpLoggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BOBY);


                    defaultClient = new OkHttpClient.Builder()
                            .connectTimeout(30, TimeUnit.SECONDS)
                            .readTimeout(30, TimeUnit.SECONDS)
                            .writeTimeout(30, TimeUnit.SECONDS)
                            .retryOnConnectionFailure(true)
                            //  .addInterceptor(new UnifiedRequestHead())
                            .addInterceptor(httpLoggingInterceptor)
                            .sslSocketFactory(socketFactory)
                            .hostnameVerifier(new HostnameVerifier() {
                                @Override
                                public boolean verify(String hostname, SSLSession session) {
                                    return true;
                                }
                            })
                            .build();
                }
            }
        }
        return defaultClient;
    }

}

Step7: SeviceFactory

import android.content.Context;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
import retrofit2.converter.gson.GsonConverterFactory;

public class ServiceFactory {
    private static String BASE_URL="http://192.168.137.1:8081/";      //ip地址
    public static int NET_SUCCESS_CODE=200;         // 请求成功返回的code
    private static ServiceFactory serviceFactory;

    private ApiService apiService;  //登录模块

    //单例模式
    public static ServiceFactory getServiceFactory(){
        if(serviceFactory==null){
            synchronized (ServiceFactory.class){
                if(serviceFactory==null){
                    serviceFactory=new ServiceFactory();
                }
            }
        }
        return serviceFactory;
    }

    public ApiService getApiService(Context context){
        if(apiService==null){
            synchronized (ServiceFactory.class){
                if(apiService==null){
                    Retrofit retrofit=new Retrofit.Builder()
                            .baseUrl(BASE_URL)
                            .client(OKHttpClientFactory.getDefaultOkClient())
                            .addConverterFactory(GsonConverterFactory.create())
                            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                            .build();
                    apiService=retrofit.create(ApiService.class);

                }
            }
        }
        return apiService;
    }
}

Step8: BaseModel

public class BaseModel {

    public Observable<Buyer> buyerRegister(Context context, Buyer buyer){
        return ServiceFactory.getServiceFactory()
                .getApiService(context)
                .buyerRegister(buyer)
                .compose(RxHelper.<Buyer>handleResult());
    }
}

Step9: ApiService

public interface ApiService {
    @POST("buyer/register")
    Observable<BaseResponse<Buyer>> buyerRegister(@Body Buyer buyer);

Step10：在activity或其他地方调用

 @SuppressLint("CheckResult")
    private void buyerRegister(Context context, String url, Buyer buyer){
        new BaseModel().buyerRegister(context, buyer)
                .subscribe(new Observer<Buyer>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                        Toast.makeText(context, "onSub： "+d.toString(), Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onNext(Buyer buyer) {
                        // 对返回数据进行处理
                        Toast.makeText(context, "OnNext： "+buyer.toString(), Toast.LENGTH_SHORT).show();
                        Log.d("CTB_register：", buyer.toString());
                    }

                    @Override
                    public void onError(Throwable e) {
                        // 出现错误
                        Toast.makeText(context, "error： "+e.getMessage(), Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onComplete() {
                        // 注册成功
                        Toast.makeText(context, "注册成功： ", Toast.LENGTH_SHORT).show();
                    }
                });
    }

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